The sewage produced by pharmaceutical companies is caused by the pollution of many pollutants, such as complex, toxic, harmful and biologically difficult to degrade organic substances, causing serious pollution to water bodies. At the same time, industrial sewage is also obviously acidic and alkaline, and some sewage contains excessive salt. These characteristics make pharmaceutical sewage become a kind of sewage that is difficult to handle in the water treatment industry. Pharmaceutical industry wastewater mainly includes four categories: antibiotic production wastewater, synthetic drug production wastewater, Chinese patent medicine production wastewater, and washing water and washing wastewater in various preparation processes. The wastewater is characterized by complex composition, high organic content, high toxicity, deep color and high salt content, especially poor biochemical properties, and intermittent discharge, which is an industrial wastewater that is difficult to treat. With the development of China's pharmaceutical industry, pharmaceutical wastewater has gradually become one of the important sources of pollution. How to treat this type of wastewater is a difficult problem in environmental protection today.
1. Treatment method of pharmaceutical wastewater The treatment methods of pharmaceutical wastewater can be summarized as follows: physical treatment, chemical treatment, biochemical treatment and combination treatment of various methods, etc., and various treatment methods have their own advantages and disadvantages.
1.1 Physicochemical treatment According to the water quality characteristics of pharmaceutical wastewater, physicochemical treatment is required in the treatment process as a pretreatment or post-treatment process for biochemical treatment. The currently applied physical and chemical treatment methods mainly include coagulation, air flotation, adsorption, ammonia stripping, electrolysis, ion exchange and membrane separation.
1.1.1 Coagulation method This technology is a water treatment method commonly used at home and abroad. It is widely used in the pretreatment and post-treatment of pharmaceutical wastewater, such as aluminum sulfate and polyferric sulfate for traditional Chinese medicine wastewater. The key to efficient coagulation treatment is to properly select and add coagulants with excellent performance. In recent years, the development direction of coagulants has evolved from low molecular to polymeric polymers, from a single functional to a complex. Liu Minghua and others used a high-efficiency composite flocculant F-1 to treat the wastewater of acute syrup production. When the pH was 6.5 and the flocculant dosage was 300mg/L, the COD, SS and chromaticity removal rates of the waste liquid were respectively It has 69.7%, 96.4% and 87.5%, and its performance is obviously better than single flocculant such as PAC (powdered activated carbon) and polyacrylamide (PAM).
1.1.2 Air floatation The air floatation method usually includes various forms such as inflatable air floatation, dissolved air flotation, chemical air floatation and electrolysis air floatation. Xinchang Pharmaceutical Factory uses CAF vortex air flotation device to pretreat pharmaceutical wastewater. With the appropriate agent, the average removal rate of COD is about 25%.
1.1.3 Adsorption method Commonly used adsorbents include activated carbon, activated coal, humic acid, and adsorption resin. Wuhan Jianmin Pharmaceutical Factory uses coal ash adsorption-two-stage aerobic biological treatment process to treat its wastewater. The results show that the COD removal rate of the wastewater by adsorption pretreatment is 41.1%, and the BOD5/COD value is increased.
1.1.4 Membrane separation method Membrane technology includes reverse osmosis, nanofiltration membrane and fiber membrane, which can recover useful substances and reduce the total amount of organic emissions. The main features of this technology are simple equipment, convenient operation, no phase change and chemical change, high processing efficiency and energy saving. Juanna and others used a nanofiltration membrane to separate the lincomycin wastewater, and found that it not only reduced the inhibitory effect of lincomycin on the microorganisms, but also recovered lincomycin.
1.1.5 Electrolysis method This method has been paid attention to by the treatment of wastewater with high efficiency and easy operation. At the same time, the electrolysis method has a good decolorization effect.
The riboflavin supernatant was pretreated by electrolysis, and the removal rates of COD, SS and chromaticity were 71%, 83% and 67%, respectively.
2 When chemical treatment is applied, the excessive use of certain reagents may lead to secondary pollution of water bodies. Therefore, relevant experimental research work should be done before design. Chemical methods include iron-carbon method, chemical redox method (fenton reagent, H2O2, O3), and deep oxidation technology.
1.2.1 Iron-carbon method Industrial operation shows that the biodegradability of effluent can be greatly improved by using Fe-C as a pretreatment step of pharmaceutical wastewater. Lou Maoxing et al [9] used iron-microelectrolysis-anaerobic-aerobic-air-floating combined treatment process to treat pharmaceutical intermediates such as erythromycin and ciprofloxacin, and COD removal rate after iron-carbon treatment. Up to 20%, the final effluent meets the national first-class standard of Integrated Wastewater Discharge Standard (GB8978-1996).
1.2.2 Fenton reagent treatment method The combination of ferrous salt and H2O2 is called Fenton reagent, which can effectively remove the refractory organic matter that cannot be removed by traditional wastewater treatment technology. With the deepening of the research, ultraviolet light (UV), oxalate (C2O42-) and the like are introduced into the Fenton reagent, so that the oxidation capacity is greatly enhanced. Cheng Hao et al [10] used TiO2 as a catalyst and 9W low-pressure mercury lamp as the light source. The Fenton reagent was used to treat the pharmaceutical wastewater, and the decolorization rate was 100%, the COD removal rate was 92.3%, and the nitrobenzene compound was 8.05mg. /L drops to 0.41 mg / L.
1.2.3 This method can improve the biodegradability of wastewater, and has a good removal rate for COD. For example, Balcioglu and other three antibiotic wastewaters were subjected to ozone oxidation treatment. The results showed that the ozone oxidation wastewater not only increased the ratio of BOD5/COD, but also the removal rate of COD was more than 75%.
1.2.4 Oxidation technology, also known as advanced oxidation technology, it brings together the latest research results of modern optical, electrical, acoustic, magnetic, materials and other similar disciplines, including electrochemical oxidation, wet oxidation, supercritical water oxidation, Photocatalytic oxidation and ultrasonic degradation methods.
Among them, the ultraviolet photocatalytic oxidation technology has the advantages of novelity, high efficiency, no selectivity to wastewater, especially suitable for the degradation of unsaturated hydrocarbons, and the reaction conditions are mild, no secondary pollution, and has a good application prospect. Compared with ultraviolet, heat, pressure and other treatment methods, ultrasonic treatment of organic matter is more direct and requires less equipment. As a new type of treatment method, it is receiving more and more attention. Xiao Guangquan et al [13] treated the pharmaceutical wastewater with ultrasonic-aerobic biological contact method. Under the condition of ultrasonic treatment for 60s and power of 200w, the total COD removal rate of wastewater was 96%.
1.3 Biochemical treatment Biochemical treatment technology is a widely used treatment technology for pharmaceutical wastewater, including aerobic biological method, anaerobic biological method, aerobic-anaerobic combination method.
1.3.1 Aerobic biological treatment Since most of the pharmaceutical wastewater is high-concentration organic wastewater, it is generally necessary to dilute the raw liquid when performing aerobic biological treatment, so the power consumption is large, and the wastewater is biodegradable, and it is difficult to achieve direct biochemical treatment. Emissions, so there are not many aerobic treatments alone, and pretreatment is generally required. Commonly used aerobic biological treatment methods include activated sludge method, deep well aeration method, adsorption biodegradation method (AB method), contact oxidation method, sequencing batch intermittent activated sludge method (SBR method), and circulating activated sludge method. (CASS law) and so on.
(1) Deep well aeration method Deep well aeration is a high-speed activated sludge system. This method has high oxygen utilization rate, small floor space, good treatment effect, low investment, low operating cost, no sludge expansion, and production. Low mud content and other advantages. In addition, its heat preservation effect is good, and the treatment is not affected by climatic conditions, which can ensure the effect of winter wastewater treatment in the northern region. After the high-concentration organic wastewater from the Northeast Pharmaceutical Plant was biochemically treated in the deep well aeration tank, the COD removal rate reached 92.7%. It can be seen that the treatment efficiency is very high, and it is extremely beneficial to the next step of treatment. Play a decisive role.
(2) AB method AB method is an ultra-high load activated sludge method. The removal rate of BOD5, COD, SS, phosphorus and ammonia nitrogen by AB process is generally higher than that of conventional activated sludge process. Its outstanding advantages are high load in section A, strong impact load resistance, large buffering effect on pH and toxic substances, and especially suitable for treating wastewater with high concentration and large changes in water quality and quantity. Yang Junshi and others used the hydrolysis acidification-AB biological process to treat antibiotic wastewater. The process is short, energy saving, and the treatment cost is lower than the chemical flocculation-biological treatment method of the same kind of wastewater.
(3) Biological contact oxidation method This technology combines the advantages of activated sludge and biofilm method, and has the advantages of high volumetric load, low sludge production, strong impact resistance, stable process operation and convenient management. Many projects use a two-stage method, which aims to acclimate the dominant strains at different stages, give full play to the synergy between different microbial populations, and improve biochemical effects and impact resistance. In the engineering, anaerobic digestion and acidification are often used as pretreatment steps, and the contact oxidation process is used to treat pharmaceutical wastewater. Harbin North Pharmaceutical Factory used hydrolysis acidification-two-stage biological contact oxidation process to treat pharmaceutical wastewater. The operation results show that the treatment effect is stable and the process combination is reasonable. With the gradual maturity of the process technology, the application field is also more extensive.
(4) SBR method SBR method has strong impact load resistance, high sludge activity, simple structure, no need for reflow, flexible operation, less land occupation, low investment, stable operation, high matrix removal rate, good nitrogen and phosphorus removal effect, etc. It is suitable for treating wastewater with large fluctuations in water quality.
Wang Zhong's experiment on treating pharmaceutical wastewater with SBR process shows that the aeration time has a great influence on the treatment effect of the process; setting the anoxic section, especially the repeated design of anoxic and aerobic, can significantly improve the treatment effect; The SBR strengthening treatment process of CIC plus PAC can significantly improve the removal effect of the system. In recent years, the process has become more and more perfect, and it has been widely used in the treatment of pharmaceutical wastewater. Qiu Lijun and others used the hydrolysis acidification-SBR method to treat biopharmaceutical wastewater, and the effluent quality reached the first grade standard of GB8978-1996.
1.3.2 Anaerobic biological treatment At present, the treatment of high-concentration organic wastewater at home and abroad is mainly based on anaerobic method, but the effluent COD is still high after treatment by separate anaerobic method, and generally requires post-treatment (such as aerobic biological treatment). ). At present, it is still necessary to strengthen the development and design of high-efficiency anaerobic reactors and conduct in-depth study of operating conditions. The most successful applications in the treatment of pharmaceutical wastewater are upflow anaerobic sludge blanket (UASB), anaerobic composite bed (UBF), anaerobic baffled reactor (ABR), hydrolysis, and the like. For those who need to treat pharmaceutical wastewater, they can also consult the sewage treatment project service platform for companies with similar experience in wastewater treatment.
(1) UASB method UASB reactor has the advantages of high anaerobic digestion efficiency, simple structure, short hydraulic retention time, no need for separate sludge reflux device, etc. UASB treatment of kanamycin, chlorin, VC, SD and glucose When pharmaceutical wastewater is produced, it is usually required that the SS content should not be too high to ensure that the COD removal rate is above 85% to 90%. The COD removal rate of the two-stage series UASB can reach more than 90%.
2) UBF method, such as Buyin Wenning, compared the UASB and UBF. The results show that UBF has the characteristics of good mass transfer and separation effect, large biomass and biological species, high processing efficiency and strong operational stability. A practical and efficient anaerobic bioreactor.
(3) Hydrolysis acidification method The hydrolysis tank is called a hydrolyzed upflow sludge bed (HUSB), which is an improved UASB. Compared with the whole process anaerobic tank, the hydrolysis tank has the following advantages: no need to seal, stir, no three-phase separator, which reduces the cost and facilitates maintenance; can degrade macromolecules and non-biodegradable organic substances in wastewater into small molecules. Organic matter that is easily biodegradable, improves the biodegradability of raw water; rapid reaction, small tank volume, less capital investment, and reduced sludge volume. In recent years, the hydrolysis-aerobic process has been widely used in the treatment of pharmaceutical wastewater. For example, a biopharmaceutical plant uses a hydrolysis acidification-two-stage biological contact oxidation process to treat pharmaceutical wastewater. The operation is stable and the organic matter removal effect is remarkable. COD, BOD5 The removal rates of SS and SS were 90.7%, 92.4%, and 87.6%, respectively.
1.3.3 Anaerobic-aerobic and other combined treatment processes may not meet the requirements due to separate aerobic treatment or anaerobic treatment, while anaerobic-aerobic, hydrolytic acidification-aerobic and other combined processes improve the biodegradability of wastewater. The impact resistance, investment cost, treatment effect and other aspects show significantly better performance than single processing methods, and thus have been widely used in engineering practice. For example, Limin Pharmaceutical Factory uses anaerobic-aerobic process to treat pharmaceutical wastewater, BOD5 removal rate is 98%, COD removal rate is 95%, and the treatment effect is stable; Xiao Liping uses micro-electrolysis-anaerobic hydrolysis acidification-SBR process to treat chemistry Synthetic pharmaceutical wastewater, the results show that the whole series process has strong impact resistance to wastewater water quality and water volume, COD removal rate can reach 86%～92%, which is an ideal process choice for treating pharmaceutical wastewater; Hu Dazhao et al. In the treatment of pharmaceutical intermediate pharmaceutical wastewater, the hydrolysis acidification-A/O-catalytic oxidation-contact oxidation process is adopted. When the influent COD is about 12000 mg/L, the effluent COD is less than 300 mg/L; Xu Meiying et al. adopt biofilm- The SBR process for the treatment of pharmaceutical wastewater containing biodegradable materials can achieve a COD removal rate of 87.5% to 98.31%, which is much higher than that of the biofilm method and the SBR method alone.
In addition, with the continuous development of membrane technology, the application research of membrane bioreactor (MBR) in pharmaceutical wastewater treatment has gradually deepened. MBR combines the characteristics of membrane separation technology and biological treatment, and has the advantages of high volumetric load, strong impact resistance, small floor space and less residual sludge. Bai Xiaohui and others used an anaerobic-membrane bioreactor process to treat a pharmaceutical intermediate acid chloride wastewater with a COD of 25000 mg/L. The ZKM-W0.5T membrane module produced by Hangzhou Chemical Membrane Engineering Co., Ltd. was used to maintain the COD removal rate. More than 90%; Livinggston et al. used the ability of specific bacteria to degrade specific organic matter, and firstly used an extraction membrane bioreactor to treat industrial wastewater containing 3,4-dichloroaniline. HRT was 2h, and the removal rate reached 99%. The ideal processing effect. Despite the problems in membrane fouling, with the continuous development of membrane technology, MBR will be more widely used in the field of pharmaceutical wastewater treatment.
2. Treatment process and selection of pharmaceutical wastewater The water quality characteristics of pharmaceutical wastewater make it impossible for most pharmaceutical wastewater to be treated by biochemical treatment alone, so necessary pretreatment must be carried out before biochemical treatment. Generally, a regulating tank should be set to adjust the water quality and pH, and according to the actual situation, a physicochemical or chemical method is used as a pretreatment process to reduce the SS, salinity and partial COD in the water, and reduce the biological inhibitory substances in the wastewater, and Improve the degradability of wastewater to facilitate subsequent biochemical treatment of wastewater.
The pretreated wastewater can be treated according to its water quality characteristics by an anaerobic and aerobic process. If the effluent requirements are high, the aerobic treatment process should be continued after the aerobic treatment process. The choice of specific process should take into account the nature of the wastewater, the treatment effect of the process, infrastructure investment and operation and maintenance, etc., so that the technology is feasible and economically reasonable. The overall process route is a pretreatment-anaerobic-aerobic- (post-treatment) combination process. For example, Chen Minghui used a hydrolysis adsorption-contact oxidation-filtration combination process to treat the comprehensive pharmaceutical wastewater containing artificial insulin. After treatment, the effluent quality was better than the primary standard of GB8978-1996. Air flotation-hydrolysis-contact oxidation process for chemical pharmaceutical wastewater, composite micro-oxygen hydrolysis-composite aerobic-sand filtration process for antibiotic wastewater, air flotation-UBF-CASS process for treatment of high-concentration Chinese medicine extraction wastewater, etc. effect.
3. Recycling of useful materials in pharmaceutical wastewater Promote clean production in the pharmaceutical industry, improve the utilization rate of raw materials and the comprehensive recovery rate of intermediate products and by-products, and reduce or eliminate pollution in the production process through reforming processes. Due to the particularity of certain pharmaceutical production processes, the wastewater contains a large amount of recyclable materials. For the treatment of such pharmaceutical wastewater, material recovery and comprehensive utilization should be strengthened first. For example, Zhejiang Yiwu Huayi Pharmaceutical Co., Ltd. uses a fixed scraper film to evaporate, concentrate, crystallize and recover (NH4)2SO4 with a mass fraction of about 30%, for the ammonium salt content of its pharmaceutical intermediate wastewater is as high as 5%~10%. NH4NO3 is used as fertilizer or reuse, which has obvious economic benefits. A high-tech pharmaceutical company uses blow-off method to treat production wastewater with extremely high formaldehyde content. After recovery, formaldehyde gas can be formulated into formalin reagent or burned as boiler heat source. . Through the recovery of formaldehyde, the resources can be used sustainably, and the investment cost of the treatment station can be recovered within 4 to 5 years [33], achieving the unification of environmental and economic benefits. However, in general, pharmaceutical wastewater has complex composition, is difficult to recycle, and has a complicated recycling process and high cost. Therefore, advanced and efficient integrated wastewater treatment technology is the key to completely solve the wastewater problem.